1. Field of the Invention
This invention relates to a coupled pipe assembly wherein the opposed ends of pipes having an internal coating or lining of corrosion-resistant material are joined by welding. An internal sleeve is used in association with the coupled pipe ends to protect the corrosion-resistant lining of the pipes from heat damage incident to the welding operation. For this purpose, the internal sleeve has an internal corrosion-resistance lining. Each end of the sleeve has a tapered cross-section forming a rounded edge portion.
2. Description of the Prior Art
In various applications, such as in the oil and gas industry, there is a need for alloy pipe, such as steel pipe, provided with a lining of corrosion-resistant material. For this purpose, it is known to bond to the pipe interior various epoxy based materials, polyethylene, polyvinyl chloride and other thermoplastic and thermosetting materials. With pipe having these internal coatings, it is necessary to protect the homogenous integrity of the internal coating from damage from heat generated during the welding of the pipe ends. It is known for this purpose to use an internal sleeve with a heat-deflecting barrier positioned adjacent the weld zone of the opposed pipe ends. Coupled pipe assemblies of this type are disclosed in Abbema et al., U.S. Pat. No. 4,913,465 issued Apr. 3, 1990.
With conventional assemblies of this type, during welding of the pipe ends the integrity of the corrosion-resistant lining in the pipe is destroyed, particularly at portions near the weld.
With coupled pipe assemblies including the coupled pipe assembly of the aforementioned patent, it is necessary to inspect the assembled pipeline for discontinuities, such as cracks, corrosion, body wall loss and the like. This is typically achieved by ultrasonic techniques. For this purpose, a transducer is inserted through the pipeline to the coupling thereof. With assemblies having internal sleeves used to replace the interior corrosion-resistance coating of the pipes during welding, effective insertion and removal of the transducer is impaired by the sleeve. Specifically, the transducer will engage the sleeve ends to prevent the end of the transducer from passing beyond the sleeve. This may result in damage to the transducer, damage to the internal coating within the pipeline, the sleeve or both, and overall renders a "smart pigging" inspection operation impossible. In addition, the sleeve ends increase the coefficient of friction of the fluid flowing through the pipe and against the internal pipe wall. This substantially increases the erosion of the pipe. Pipe wear is also caused by the hydraulic shock resulting from the sudden change in velocity resulting when the fluid flowing through the pipe contacts the sleeve ends. Likewise, the sleeve ends provide areas within the pipe for adherence of contaminates, which results in an additional affect on the fluid velocity.